Communication signaling system



H. WOODWARD 1,834,265

ING SYSTEM Dec. 1, 1931.

COMMUNICATION SIGNAL Filed June 30, 1930 INVENTOR MARION H WOODWARD MW ATTO EY Patented Dec. 1, 1931 UNITED STATES NEW YORK PATENT OFFICE MA RION H. WOODWARD, OF BROOKLYN, NEW YORK, ASSIGNOR TO INTERNATIONAL COMMUNICATIONS LABORATORIES, INC.,

OF NEW YORK, N. Y., A CORPORATION OF COMMUNICATION SIGNALING SYSTEM Application filed June 80,

This invention relates to signaling systems for use in cable, radio or land-line telegraphy or in the combined use of any of these means of communication. The object of the invention is directed particularly toward improvement in the transmitting and receiving instruments and in the adaption of the same for more clearly communicating messages and avoiding the eflect of line interference.

A further object is to provide simpler equipment at repeating stations for land lines over which cable code messages may be relayed, thus rendering it easier to maintain. q i

In the use of repeating equipment, particularly where messages have to be relayed from a cable to a land line or vice versa', difiiculties have frequently been encountered in the maintenance of proper adjustments of the relays themselves so that they will not.be subject to extraneous line interference. One

well-known cable code it is the practice to employ time intervals of zero line potential between the signaling impulses for each letter and longer time intervals of zero potential between the words. Thus, the cable-code is usually made up of three elements or kinds of signals-posit1ve for dots, negative for dashes and zero for letter and word spaces. The zero elements are articularly suscep-- tible to destructive inter erence, a fact which was realized in the early stages of telegraphy so that on land lines the difficulty was overcome by the use of polar methods instead of the open and closed method.

The present invention provides a means for utilizing the almost universally adopted cable-code while eliminating its objectionable intervals of zero line potential and substituting a line condition which is distinguishable from the dot and dash signaling impulses but which at the same time tends to minimize interference effects. i ,In carrying :out this invention the commu nicatio'ns'; circuit has impressed upon it the 'usual cable code'signalsconsisting of positivegand negative impulses and where letter or word spaces are required an alternating of the principal reasons for this is that in the 1930. Serial No. 464,961.

current of suitable frequency is used in place of the zero potential.

Several alternative embodiments of the invention are diagrammatically illustrated in the accompanying drawings in which Figure 1 shows the usual cable-code transmitter with circuits adapted tothe purpose Fig. 4 shows electrical filter arrangement v alternative to that shown in Fig. 3.

Fig. shows an adaptation of this invention to the requirements of a repeater sta tion.

Fig. 6 shows a repeater station adaptation alternative to that shown in Fig. 5.

In the various embodiments of this invention a similar method of modifying the transmitted signals will be apparent. The essence of the invention ismore in the method than in the means employed. In fact it has been discovered that new and advantageous results are obtainable from certain minor adjustments which can be made on transmitting and receiving equipment of the well-known types. More particularly is this true in respect to the use of the standard Gulstadt arrangement for transmission, as will be more clearly brought outin this specification.

In Fig. 1 the transmitter is shown. In this case it comprises two relays l and 2, relay 1 having three windings 34, 5'6, and 78,

and relay 2 having a winding 1617. The usual method-.- of transmission'is to apply positive potential to the transmitting contact 18 for a dot signal and to the contact 19 fora dashsignal. Whenthe impulse is taken at contact 18 there follows a drop of potential in winding 3-4 from terminal 3 to terminal 4, this causingthe armature tongue 11 to move against contact 12. Positive potential is thus applied from the source 20 through resistance 10 to terminal 6 of winding 6'5; also to terminal "of winding 7 8. The energizing Qforces ofthese two windings oppose one another during the moment that condenser 9 receives a charge. After that,, the winding 65 remains energi'zed in opposition to the force of winding and when the latter is de-energized the winding 6-5 first acts alone in breaking contact between armature 11 and contact 12, then its force is boosted bythe series connection with winding 8-7, both windings receiving the discharge of the condenser 9 and assing the same through the resistance 15 an conductor 18 back to the opposite side of the condenser. The result is that the motion of armature 11 is considerably accelerated at the end of a dot or. dash signal, or when the winding 3- 1 receives a reversal of c111 rent.

The operation of the relay 1 when a dash signal is to'be transmitted is brought about .by impressing positive potential on the contact 19, in which case the movement of armature tongue 11 is against contact 13 and all the actions and reactions of the windings 34 56, 7-8 and condenser9 are just reverse from those in effect in the transmission of a dot signal.

Following this arrangement further, it'will be seen that relay 2 is controlled by relay 1 in this manner: if one or more successive dot signals are to be transmitted, current flows from the positive pole of the source 20 through contact 12, armature 11 and resistance 14 to. terminal 16 of the winding in relay 2, thence .back to the neutral pole of source 20. Relay winding 16-17 when energized by current in this direction throws its armature 21 against contact 22, thus feeding positive potential to the line or cable 24, the neutral potential be ing permanently grounded-at 25. This is the usual practice in transmitting a positive impulse to represent a dot and a negative im pulse to represent a dash. The ordinary transmitting device, however, is somewhat different from that shown in Fig. 1 in that provision is made for space signals during which zero-potential is applied to line 24.

It has been the common practice heretofore in operating repeater stations'to provide pulsating regenerators sensitive to the incoming signals and adaptedto definitely time the duration of the repeated signals. Thus the regenerator has a natural beat frequency correspondin with the si aling unit. The

' Gulstadt r evice is so use in land-line telegraphy to provide a natural beat frequency equal to 'the unit signal frequency, and to minimize the travel time of the relay armatures by the use of a condenser and resistance of suitablewalues in series respectively with the relay windings. The present invention makes use of a new practice in the employment of such valuesfor the resistance15 and the condenser 9 that a current of greater frequency than the dot and dash signaling frequency will be set up on the line during the lapse of a space signal. The operation is as follows:

A relatively small capacity value for condenser 9 and a relatively low resistance 15are chosen. During a space signal when no currentis flowing through winding 3-4, the condenser 9 charges and discharges rapidly as compared with the time constants of the dot and dash signals. The condenser charge is continually reversed by the vibration of armature 11 between the contacts 12 and 13 which are connected respectively to opposite polesof the source 20. The relay armature 21 is caused to vibrate in synchronism with armature 11, since the winding 16-17 of relay 2 receives part of the current flow in space signaling frequency is interrupted by} closing either of the contacts 18 or 19 against the positive source of potential to transmit dot or dash signals. It is obvious that the ener izing'efiect of a curent flow throu h win ing 3-4 can be made to suppress t e frequenc set up in windings 5-6 and 7 8. Hence, t is arrangement has no disturbing effect upon the operation of the transmitter in sending dot and dash signals.

Comparison of line'signals accordin J to past practice and as obtained in the emp oyment of this invention may be observednn the two graphic representations of signals shown in Fig.2. In both gra hs the, dot signals are indicated at A; and dash signals at B. The positive pulse C represents three dots in succession. At D a short spacing signal occurs as between letters and at E a longer spacing signal as between words. The zero .line potential of these spacing signals D and E is replaced in the other graph by an alternating current cdndition as at F. The idea of impressin this frequency on the line automatically w enever there 1s a pausein the transmission of dots and dashes constitutes the essence of this invention.

' Receptive means are shown in Fig. 3 for recording the dot and dash signals and filtering out the space signals of higher frequency. The line 24 is connected to rela winding 27, the other side of which is groun ed. The relay armature 28 responds to each of the three elements of the signals, dots, dashes and'spaces, 'vibrating'rapidly on reception of the latter. The recorder coil 29 is tuned by adjustingthe'stifl'ness of its suspension so that it will respond to the funds,- mental signal frequency. of-the dots and dashes only. This coil derives its'energy from the source 32 and obviously the twoance of coils acting in conjunction with the condenser 31 filters out the space signaling frequency'such as might be used preferably on a land line. Thus, in the output circuit which 15 might be connected to a cable the condition of zero line potential for space signals would be.

automatically restored.

Fig. 5 shows re-transmitting relays 34 and 35 connected between the points R. R. of the output circuit which otherwise is the same as shown in Fig. 4. The filtering out of alternating current for space signals takes place through the inductances 30. Belay 34: being polarized responds only to dash signals and relay 35 only to clot signals. Their armatures 36 and 37 are shown in the neutral position when zero potential is impressed upon the line. Upon reception of a dot signal over line .24, armature 28 swings against the positivelypoled contact 33, relay 35 operates to throw its armature 37 against contact 38 to ground the negative side of the battery 39. Positive battery already connected to the cable 40 through relay armature 36 provides the posi- 34loperates similarly to transmit a dash signa Fig. 6 shows the filtering effect of two slowacting relays A1 and 42, one for dash signals 0 and one for dot signals. These are .so adjusted that they will not respond to the high vibrating frequency but respond perfectly to the low signaling frequency. This circuit may also be used at a repeater station between a land line and a cable.

It is obvious that communications received over a cable in cable code (that is, with zero potential signals for spaces) can be translated into the modified cable code with high frequency space signals for transmission over land lines, use being made of the transmitting means similar to that shown in Fig. 1. In this case it will be understood that the signals received over the cable would be utilized to actuate tworelays one for closing contacts as at 18 to transmit a dot and the other for closing contacts as at 19 to transmit a dash.

WVhat is claimed is:

1. In a communications system the method of code transmission which consists in impressing upon the transmitting medium at a predetermined basic frequency a series of intelligence bearing signals separable by but not overlapped by non-intelligible spacing signals ofa different frequency.

output circuit either a recorder 29 or a re-' peater relay may be connected. The imped- 5 tive impulse required for a dot signal. Relay sistance to a frequency different from 2. In a communications system means to codify the intelligence to be transmitted from one station to another which comprises two signal-element initiators, one for signals oi dot-significance; the other for signals of dashsignificance, and means rendered operative when neither dot nor dash is being signaled to maintain 'a. third signal-element as a preventer of interference effects between the two stations,

' 3. In a communications system a transmitter comprising means to impress intelligence bearing signals upon a circuit at a predetermined basic frequency, and means to maintain the circuit unimpaired by extraneous 1nterferenc'e during intervals between said signals by impressing upon the circuit a current \of another frequency, the units of which are non-intelligible.

4. In a communications system, a transmitter comprising a plurality of contact points each for initiating a distinctive signal, a relay including a plurality of energizing coils, one of said coilsbeing connected with said contact points, two other coils being in series in a closed circuit which includes a resistance and a condenser, connections at the mid-point betwen these two coils through the relay tongue and its contacts with opposite poles of an energy source, a shunt circuit including a second relay coil between said relay tongue and a neutraltap from said en'- ergy source, and means to adjust the timing characteristicsof the said condenser and 1:-

t e basic signaling frequency.

5. In a communications system, a telegraph circuit, means to impress upon said circuit successively a 'basic signaling frequency and a non-intelligible spacing frequency "and receptive means comprlsing a filter to suppress the spacing frequency.

6. In a communications system a receiving relay comprising connections between a source of energy and the contact points associated' with the relay armature tongue; an output circuit which includes the relay armature tongue, a-filter, a recording orrepeating instrument and a neutral point.

.tap from said source of energy; and means to adjust the recording or repeating instrument to render it responsive to a predetermined basic signaling frequency and non-responsive to a non-intelli 'ble spacing frequency intermittently recelved by said relay.

7. In a communications system a receiver responsive to. intelligence-bearin signals transmitted at a single predetermmed basic frequency, a filter ada ted to' suppress all spacing signals of a di erent frequency, intermittently transmitted, and a regenerative instrument adapted to repeat only theintelligence-bearing signals. 4

8. In a communications system a receiver responsive to" intelligence-bearing signals transmitted at a predetermined basic frequency and separated by spacing signals of zero potential, a telegraph circuit and means to impress upon the same a regeneration of said intelligencebearing signals se arated by non-intelligible spacing signals 0 a frequency other than thesaid basic frequency. 9. In a communications system repeating equipment comprising a. receiving relay, a 10 filter for suppressing other than intelligencebearing signals, a plurality of repeating relays each responsive to a predetermined signal characteristic and means employed upon reception of intelligence-bearing signals such 5 as are separated by spacing signals of other than zero-potent1al-character1stic to retrainsmit onlythe intelligence-bearing signa s.

10. In a communications system, means for translating the zero units in a three-element code into a series of positive and ne ative units of shorter duration than the ot er signaling elements of said code.

11. In a communications system, the meth- 25 od of eliniinatinginterference effects therein comprising impressing positive, negative and zero signaling units on the line and transforming the zero units into a series of positive and negative units of shorter dura: tion than the other signaling units. 12. In a communications system, means for translating the zero elements in a three-element code into a series of positive and negative units ofshorterdurationthan the other as signaling units of said code,,and means for re-translating said 'positive and negative units into zero element's.

13. In a communications system, the meth-' 0d of code transmission comprising impressing upon the transmitting medium in any desired order but at a predetermined basic frequency positive and negative signal units se arable by but not overlapped by a series 0 alternate positive and negative units of a 45 different frequency.

In witness whereof, I hereunto subscribe my name this 26th day of June 1930.

MARION H. wodDWARn. 

